1. Field of the Invention
The present invention relates to a solid-state image sensing apparatus, a control method therefor, an image sensing apparatus, the basic layout of a photoelectric conversion cell, and a storage medium.
2. Description of the Related Art
In recent years, needs for processing images in computers are abruptly increasing. To meet this, many digital cameras for capturing an image into a computer are now available. Along with the development of such digital cameras, digital still cameras for processing still images tend to increase in the number of pixels. Cameras having an image sensing element of 800,000 pixels (XGA class) are spread though general moving image (video movie) cameras have an image sensing element of 250,000 to 400,000 pixels. Further, cameras having 1,000,000 pixels to 1,500,000 pixels are becoming popular. For high-end devices of an interchangeable lens type, cameras using a megapixel image sensing element having 2,000,000 pixels, 4,000,000 pixels, or 6,000,000 pixels are commercially available.
In the video movie camera, the camera photographing system such as the AF and AE of a camera is controlled using output signals successively output from an image sensing element at a video rate. For this purpose, AF adopts TV-AF (hill climbing method or contrast method).
To the contrary, the digital still camera adopts various methods depending on the number of pixels and the camera operation method. Generally in most of digital still cameras of a 250,000- or 400,000-pixel class used in the video movie camera, repetitive readout signals (images) from a sensor are displayed (to be referred to as a finder mode or EVF mode) on a color liquid crystal display (a TFT liquid crystal display of about 2 inches is recently often used) mounted on the camera. Thus, the digital still camera operates basically similarly to the video movie camera, and employs the same method as the video movie camera.
However, in a digital still camera having an image sensing element of an 800,000-pixel class or more (to be referred to as a megapixel digital still camera), the image sensing element in the finder mode operates according to a driving method of thinning out signals as much as possible, except for those from signal lines or pixels necessary for display on the liquid crystal display in order to increase the finder rate (close to the video rate).
In a high-grade digital still camera having 1,000,000 pixels or more, the time from depression of a release switch to photographing must be short in order to meet need for instantaneously photographing a still image similarly to a silver halide camera.
For these reasons, the megapixel digital still camera adopts various AF and AE methods as follows.
(1) AF
(a) The digital still camera employs an AF sensor in addition to the image sensing element. The AF sensor is of a phase difference type, contrast type, rangefinder type, active type, like the silver halide camera.
(b) The digital still camera uses an output from the image sensing element itself. In this case, the image sensing element is of a hill climbing type or phase difference type using a signal from only a specific region of the image sensing element (signals from this region are not thinned out) because a long time is spent for a read from all the pixels of the image sensing element, and distance measurement does not require information of all the pixels.
(2) AE
(a) The digital still camera employs an AE sensor in addition to the image sensing element.
(b) The digital still camera uses an output from the image sensing element itself.
However, the conventional megapixel digital still camera suffers the following problems.
As for AF, the digital still camera having an AF sensor in addition to the image sensing element requires a lens system for forming an image on the sensor, and a mechanism for realizing a corresponding AF method (for example, the active method requires an infrared generator, projection lens, light-receiving sensor, light-receiving lens, and infrared projection moving mechanism, and the phase difference method requires an imaging lens to a distance measurement sensor and a glass lens for causing a phase difference). This increases the camera size and cost. Further, AF using the image sensing element itself suffers many error factors such as the difference in path between an optical system for the image sensing element and an optical system for the AF sensor, a manufacturing error in molded members for forming these respective optical systems, and an error caused by temperature expansion. These error components are larger in the digital still camera of the interchangeable lens type than in a digital still camera of a permanent lens type.
Considering this situation, demands have arisen for digital still camera of another AF type which uses an output from the image sensing element itself. Of the AF methods, the hill climbing method is disadvantageous in a long in-focus time. The present applicant proposes a method of arranging a mechanism of moving pupil positions to positions symmetrical about the optical axis in a lens system for forming an image on an image sensing element, and calculating the defocus amount from the phase difference between images formed via the pupils, thereby adjusting the focus of the lens (Japanese Patent Laid-Open No. 9-43507). This method realizes high-speed, high-precision AF (for AF, the signal readout time is short because signals are read out from several specific lines in the image sensing element whereas the signals of the remaining lines are cleared at a high speed.) However, this method requires a mechanism for moving the pupils, resulting in large volume and high cost.
This also applies to AE because the digital still camera having an AE sensor in addition to the image sensing element requires a mechanism for the AE sensor. To use signal charges from the image sensing element itself, the image sensing element must be driven for photometry a plurality of number of times by changing the stop diameter or shutter speed because of a small dynamic range of the image sensing element. This increases the time before actual photographing, and serial movement of the stop increases power consumption.
The present invention has been made to solve the above problems, and has as its object to provide a solid-state image sensing apparatus capable of performing high-precision image sensing adjustment (for example: AF and AE) without adding any camera mechanism or increasing power consumption, a control method therefor, an image sensing apparatus, the basic layout of a photoelectric conversion cell, and a storage medium.
To solve the above problems and achieve the above object, a solid-state image sensing apparatus according to the first aspect of the present invention has the following arrangement.
That is, a solid-state image sensing apparatus in which photoelectric conversion cells for converting an optical image formed by an optical system into an electrical signal are two-dimensionally laid out is characterized in that at least some of the photoelectric conversion cells output signals not for forming an image signal.
A solid-state image sensing apparatus according to the second aspect of the present invention has the following arrangement.
That is, a solid-state image sensing apparatus having an image sensing region where photoelectric conversion cells for converting an optical image formed by an optical system into an electrical signal are two-dimensionally laid out is characterized in that the image sensing region is defined by repetition of basic layouts of photoelectric conversion cells for detecting a plurality of colors, and one photoelectric conversion cell in at least some basic layouts of the image sensing region outputs a signal not for forming an image signal.
The basic layout of a photoelectric conversion cell according to the present invention has the following layout.
That is, a basic layout of a photoelectric conversion cell in a solid-state image sensing apparatus having an image sensing region where photoelectric conversion cells for converting an optical image formed by an optical system into an electrical signal are two-dimensionally laid out is characterized in that photoelectric conversion cells for detecting a plurality of colors, and photoelectric conversion cells for outputting signals not for forming an image signal are combined.
A solid-state image sensing apparatus according to the third aspect of the present invention has the following arrangement.
That is, a solid-state image sensing apparatus in which photoelectric conversion cells for converting an optical image into an electrical signal are two-dimensionally laid out is characterized by comprising a first photoelectric conversion cell for outputting a luminance signal for forming a two-dimensional image, or a signal for generating a luminance signal and chrominance signals, a second photoelectric conversion cell for outputting a signal other than the luminance signal or the signal for generating the luminance signal and chrominance signals, and switching means for switching a first read mode of reading out a signal including both the signal output from the first photoelectric conversion cell and the signal output from the second photoelectric conversion cell, and a second read mode of reading out a signal including not the signal read out from the second photoelectric conversion cell but the signal read out from the first photoelectric conversion cell.
An image sensing apparatus according to the first aspect of the present invention has the following arrangement.
That is, an image sensing apparatus is characterized by comprising a solid-state image sensing element in which photoelectric conversion cells for converting an optical image into an electrical signal are two-dimensionally laid out, the solid-state image sensing element having a first photoelectric conversion cell for outputting a luminance signal for forming a two-dimensional image, or a signal for generating a luminance signal and chrominance signals, and a second photoelectric conversion cell for outputting a signal other than the luminance signal or the signal for generating the luminance signal and chrominance signals, a timing generator for generating a driving signal to the solid-state image sensing element, the timing generator generating a first driving signal for outputting, from the image sensing element, a signal including both the signal output from the first photoelectric conversion cell and the signal output from the second photoelectric conversion cell, and a second driving signal for outputting, from the image sensing element, a signal including not the signal read out from the second photoelectric conversion cell but the signal read out from the first photoelectric conversion cell, and switching means for switching a first photographing mode of generating a video signal using all pixels on the image sensing element by the first driving signal, and a second photographing mode of generating a video signal by thinning out the pixels on the image sensing element by the second driving signal.
An image sensing apparatus according to the second aspect of the present invention has the following arrangement.
That is, an image sensing apparatus is characterized by comprising a solid-state image sensing element in which photoelectric conversion cells for converting an optical image into an electrical signal are two-dimensionally laid out, the solid-state image sensing element having a first photoelectric conversion cell for outputting a luminance signal for forming a two-dimensional image, or a signal for generating a luminance signal and chrominance signals, and a second photoelectric conversion cell for outputting a signal other than the luminance signal or the signal for generating the luminance signal and chrominance signals, a thinning circuit for thinning image signals every predetermined time, and switching means for switching a first photographing mode of generating a video signal using all pixels on the image sensing element, and a second photographing mode of generating a video signal by abandoning signals output from the second photoelectric conversion cell by the thinning circuit, and thinning out the pixels on the image sensing element.
A solid-state image sensing apparatus control method according to the present invention has the following steps.
That is, a solid-state image sensing apparatus control method of controlling a solid-state image sensing element having a first photoelectric conversion cell for outputting a luminance signal for forming a two-dimensional image, or a signal for generating a luminance signal and chrominance signals, and a second photoelectric conversion cell for outputting a signal other than the luminance signal or the signal for generating the luminance signal and chrominance signals in a solid-state image sensing apparatus in which photoelectric conversion cells for converting an optical image into an electrical signal are two-dimensionally laid out is characterized by comprising controlling to switch a first read mode of reading out a signal including both the signal output from the first photoelectric conversion cell and the signal output from the second photoelectric conversion cell, and a second read mode of reading out a signal including not the signal read out from the second photoelectric conversion cell but the signal read out from the first photoelectric conversion cell.
A storage medium according to the present invention has the following control program.
That is, a storage medium storing a control program for controlling a solid-state image sensing element having a first photoelectric conversion cell for outputting a luminance signal for forming a two-dimensional image, or a signal for generating a luminance signal and chrominance-signals, and a second photoelectric conversion cell for outputting a signal other than the luminance signal or the signal for generating the luminance signal and chrominance signals in a solid-state image sensing apparatus in which photoelectric conversion cells for converting an optical image into an electrical signal are two-dimensionally laid out is characterized in that the control program comprises a code of the step of switching a first read mode of reading out a signal including both the signal output from the first photoelectric conversion cell and the signal output from the second photoelectric conversion cell, and a second read mode of reading out a signal including not the signal read out from the second photoelectric conversion cell but the signal read out from the first photoelectric conversion cell.
An image sensing apparatus according to the third aspect of the present invention has the following arrangement.
That is, an image sensing apparatus is characterized by comprising an image sensing region where photoelectric conversion cells for converting an optical image into an electrical signal are two-dimensionally laid out, the image sensing region including a plurality of photoelectric conversion cells for outputting signals for generating image signals, and second photoelectric conversion cells for outputting signals not for forming an image signal.
Other objects and advantages besides those discussed above shall be apparent to those skilled in the art from the description of a preferred embodiment of the invention which follows. In the description, reference is made to accompanying drawings, which form a part hereof, and which illustrate an example of the invention. Such example, however, is not exhaustive of the various embodiments of the invention, and therefore reference is made to the claims which follow the description for determining the scope of the invention.